The development of high-brightness solid state light sources, such as light emitting diodes (LEDs) and the like, has led to use of such devices in various lighting applications and apparatus. In general, a lamp or a fixture that uses a solid state light source operates in a fundamentally different way than a lamp or a fixture that uses an incandescent light source or a gas discharge light source. The primary difference in operation is that a lighting apparatus with a solid state light source operates on drive circuitry (also referred to throughout as a driver and/or driver circuit and/or driver circuitry) that is designed to drive the particular type of solid state light source being used, such as but not limited to one or more high-power LEDs.
The driver circuitry for a lighting apparatus using a solid state light source typically converts an alternating current (AC) input, such as a 120V/60 Hz line input, to a stable direct current (DC) voltage. Such circuitry typically includes a rectifier, or equivalent circuitry, and a DC-DC converter circuit, or equivalent circuitry. The rectifier receives the AC input and provides an unregulated DC output. The DC-DC converter circuit receives the unregulated DC output from the rectifier and provides a stable, regulated DC output to the solid state light source.
A variety of DC-DC converter circuit configurations are well-known in the art. Certain types of known DC-DC converter circuit configurations, such as but not limited to buck converters, boost converters, buck-boost converters, etc., are generally categorized as switching regulators. These devices include a switch, e.g. a transistor, which is selectively operated to allow energy to be stored in an energy storage device, e.g. an inductor, and then transferred to one or more filter capacitors. The one or more filter capacitors provide a relatively smooth DC output voltage to the load (i.e., the solid state light source) and provide essentially continuous energy to the load between energy storage cycles.